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A1(M) Doncaster By-Pass

Situated on the Great North Road and on the direct railway route from London to the North, Doncaster had become an important railway and industrial centre in the midst of the Yorkshire coalfields. The problems of subsidence from coal mining activities, the number of railway crossings and the River Don were leading factors in the design and routing of the by-pass motorway.

In the case of the Doncaster By-pass, having decided that the route was to be on the western side of the town due mainly to national road planning but influenced also by agricultural interests, there were three fixed points to establish as the first steps in determining the line. These consisted of the southern terminus in Nottinghamshire, the northern terminus providing a junction with the existing A1 and the crossing of the River Don.

The southern terminus, 2¼ miles south of the West Riding County Boundary on the Bawtry - Nottingham Trunk Road A614 links with the new Blyth By-pass and the recently improved existing road system joining the A1 at Markham Moor.

The northern terminus was chosen at the junction of the A1 and Redhouse - Wakefield Trunk Road A638 which was clear of the urban development north of Doncaster.

The Don Crossing more or less fixed itself. A cursory study of the local geography showed it to be the only possible crossing within reasonable distance west of town, it being on the western fringe of the suburban development and just to the east of an extensive deep quarry system. Any other crossing would have involved either major property demolition or major structural works, both of which were prohibitive.

Warmsworth junction

It was not possible to make this bridge straight over its full length owing to the curve of the motorway through Warmsworth and the last three spans on the south side of the river are on both a horizontal and vertical curve."

Proceeding northwards the by-pass runs close to the once Saxon villages of Wadworth, Spotborough, Pickburn and Brodsworth, before rejoining the Great North road at Redhouse. The 12½ mile by-pass was at the time the largest single project to be undertaken by the government to upgrade the Trunk Road A1 into a national highway suited to the needs of modern traffic.

The line of the Doncaster Motorway was confirmed in the spring of 1957 and in July of the same year the Minister of Transport invited the West Riding County Council to act as its Agent Authority and to prepare the scheme and contract documents to tender stage.

The soils investigation for the route, including testing and reports, was undertaken by the County Laboratory. The mining surveys and subsidence predictions were carried out by the County Mining Engineers Department.

Although most of the land was acquired by negotiation it was necessary to hold a public inquiry in May 1959, presided over by the Ministry's Inspector. The acquisition of land by compulsory purchase precluded land for construction and entailed further negotiations.

In June 1959 a £5.5 million contract was signed with the Consortium of Holland Hannen and Cubitts (Great Britain) Ltd, Fitzpatrick and Son (Contractors) Ltd and Lehane, MacKenzie and Shand - the consortium to be known as Cubitts, Fitzpatrick, Shand with the Shand company operating as the sponsoring company. The site organisation was controlled by one Director and one Contracts Manager from each of the partner companies. The site organisation was self contained, operating as a single closely integrated construction unit. It included its own accounting, costing, stores and buying departments, joiners shop and steel yard in addition to its plant organisation.

With a contract time of two years, the contractor in addition to preparing surveys and programmes had to investigate the surrounding land and negotiate the buying or renting land needed for construction purposes. Although all the land require for the motorway had not been acquired construction started on the 22nd June 1959 on a 200,000 cu. yd. embankment at Cusworth Park. A two-way radio system was installed for the vital communications necessary because of the large concentration of mechanical plant.

Conferences were held with the public and authorities affected by the construction and arrangements made for temporary services. Action was taken to give least interference with the use by the public of the many roads and railways crossing the motorway. The West Riding police provided valuable assistance and advise on traffic diversions and control during construction. Side roads were diverted and at Sprotborough Road a temporary Bailey Bridge erected.

A peat bog at Tickhill some three quarters of a mile long had to be removed by two Lima 1201 draglines. A fleet of Michegan loading shovels transporting the 250,000 tons of imported sand and gravel infill.

The design of the motorway was in accordance with Ministry of Transport Standards with dual 24 ft. carriageways, a 15 ft. wide central reservation and 9 ft. hard shoulders. The curves being designed for a safe speed of 70mph. A standard side slope to cuttings of 1 in 2 was adopted with 1 in 3 in boulder clay areas. The cutting at Wadsworth with its many bridges was in magnesian limestone and side slopes were increased to 1½ in 1. Gradients were no steeper than 1 in 26 with a visibility minimum distance of 800ft. being relaxed in only one or two instances.

Drainage was by means of french drains in cuttings, both connected to main drains. Embankment drainage consisted of open ditches. Due to the probability of mining subsidence flexible jointed reinforced concrete pipes were specified for main drains and pipe culverts.

The carriageway construction was also flexible comprising an 8 in. cement bound granular base and 4 in. asphalt wearing surface. Because excavation material was magnesian limestone a minimum construction thickness of 18 in. was specified with 28 in. over boulder clay and the marles.

To the casual observer, earthworks perhaps appears to be a simple and straightforward process, but with approximately 3,000,000 cu. yds. of excavation to be carried out, varying from solid rock to peat bog, and embankments of varying volumes to be placed and compacted, the earthworks was a very complicated section of the scheme. The area of road wearing surface was 390,000 sq. yds.

There were 28 bridges on the contract which gave the West Riding bridge engineers their first opportunity to attempt some standardisation of designs.

Excluding the major bridge over the River Don there were five types of bridge: four span bridges carrying existing roads over the motorway, single span bridges carrying the motorway over existing roads, footbridges and railway bridges. There were also a number of culverts and subways. In the congested Wadworth area the motorway is spanned by three two span bridges.

The aesthetics of the designs were discussed and agreed with the County Architects Department and approved by the Royal Fine Arts Commission. The Deputy County Architect, Walker, took a keen interest in the bridge designs, gave much helpful advice and encouragement to the Bridges Sections until his retirement.

Fundamental to the design concept was the choice of simply supported spans with jacking facilities to cater for mining subsidence.

The four span overbridges consisted of three piers with skeleton abutments or bankseats if on rock. A feature of the piers was the tapering from 2ft. 6in. at the top to 1ft. 6in. at the base, with battered faces and skewed ends. The centre piers were fixed and the side piers hinged at the bottom. Generally spread footings were adopted.

The decks were formed from pre-tensioned I-beams with a wide bottom flange manufactured by the Concrete Development Co Ltd. The in situ decks have diaphragms which carry transverse post-tensioned cables to provide torsional stiffening. The outer deck beams were either post-tensioned rectangular beams or duct beams carrying a cantilevered concrete parapet into which the parapet rails were set. The cantilever parapet projecting some 2ft. was to become something of a standard feature on future bridge designs.

The reinforced concrete abutments of the single span underbridges were of the counterfort type with cantilevered wing walls. Each abutment has a vertical joint near the motorway centre line. This design was adopted to avoid the effects of differential settlement between abutment and wing walls and to cater for the effects of mining subsidence.

A unique feature developed by the West Riding was the rock face texture to exposed concrete faces. This was achieved by lining the formwork with vacuum formed plastic sheets having a light filler to maintain the shape. The blockwork effect also masked construction joints, bolt holes and shutter lines.

The decks of the underbridges have pre-tensioned inverted T-beams with in situ concrete infill transversely reinforced for spans of 30 ft. and post-tensioned T-beams for spans of 55 to 80 ft. The later beams were cast with diaphragms and the whole deck transversely post-tensioned. The Gifford-Udall-CCL System was used throughout.

Two of the footbridges are of note for their extreme slenderness. The cantilever and suspended spans were cast in situ and rest on leaf piers and bank seats. There was some concern when constructed that the public might find the bridges too dynamically sensitive. To satisfy the Engineer on this point a platoon from the local Territorial Army was marched in step at varying pace across the bridge to test its integrity before the bridge was allowed to be open for public use.

The bridges on the Doncaster motorway gave an early opportunity to adopt natural and synthetic rubber bearings, which were cheaper and simpler to fix than the traditional steel sliding plate and rocker bearings.

Copper lined bitumen membranes were used for the first time for waterproofing the bridge decks which incorporated simple tee bar expansion joints.

The Don Bridge carries the motorway over the Don Valley at a height of 70 ft. above the river. The bridge site was consequently difficult of access. Large quantities of rock were blasted on both approaches to form access roads. This major bridge 760 ft. long between abutments consists of two parallel but separate structures of seven spans. The 180 ft. river span comprises a suspended span of 100 ft. and two 40 ft. long cantilevers, the adjacent anchor spans are 100 ft. long. Of the remaining spans two are 100 ft. and two 90 ft. long.

Each carriageway is carried on five riveted steel girders and a 9 in. thick reinforced concrete deck acting compositely. The abutments of counterfort type and north pier are founded directly on underlying rock and all other piers are on bored piles. The piers are in the form of tall, slender T's with hexagonal columns. Provision was made for jacking to deal with mining subsidence.

The Braithwaite Foundation & Construction Company, as sub-contractors, undertook the bored cylindrical piles for the piers, together with the fabrication of steelwork at West Bromwich, and its site erection. The steel superstructure was assembled on the approach embankments and launched into position. The launching girders were made up from the approach span girders and a light lattice launching nose.

The five railway bridges presented a major obstacle to the completion of the contract due to the many regulations by British Railways to cover working in close proximity to the line. There are three steel decked railway underbridges and two concrete decked bridges over the motorway.

The largest bridge, Warmsworth Railway Bridge, has four spans and crosses the slip roads in addition to the motorway at the junction with the A630. Construction of these bridges involved driving sheet-piled retaining walls to enable each separate pier and abutment to be excavated and built under a temporary bridge of heavy steel joists. The single span girders of the permanent deck were assembled on suitable trestling alongside their final position, the concrete deck cast, waterproofing, ballast and the track work laid the span was then rolled into position onto the piers and abutments.

In the case of Brodworth Railway Bridge which carried heavy colliery traffic, the railway embankment was excavated during a week's holiday period at the colliery and a temporary bridge constructed to carry the line. The railway bridges were dealt with by the British Railways' Chief Civil Engineer.

Some of the largest pre-cast beams were used in the bridges carrying the motorway over the railways being 84 ft. long and weighing some 60 tons each.

The section of the Doncaster By-pass in Nottinghamshire, 2¾ miles in length, together with the Blyth By-pass, was undertaken as a separate contract. The by-pass of this historic town was opened to traffic in December 1960. The specification for the roadworks was similar to that for the West Riding section.

The southern access to the motorway is provided by a 240 ft. dia. roundabout at the junction with the Blyth By-pass and the A614 Blyth to Bawtry trunk road. Bridges carry the motorway over the Whitewater drain, the Styrrup-Harworth road B6463, the Harworth Colliery railway line and the occupation road at Common Lane. The Styrrup-Serlby Class III road is carried over the motorway on a bridge whose design was approved by the Royal Fine Art Commission. The bridges are constructed in two halves to allow for differential settlements and jacking beams have been provided to allow for future raising should this prove necessary due to mining subsidence.

The motorway also crosses the unclassified road at Styrrup but as the motorway here is in a 60 ft. cutting and a bridge would have been very expensive, a short length of new road was built connecting it with the Class III Styrrup-Serlby road. The diversion of this minor road saved a substantial amount of money.

The motorway was designed to blend in with the surrounding countryside and additional land was acquired for tree planting.

The motorway was opened in July 1961 by the Minister of Transport, the Rt. Hon. Ernest Marples.